基于正演模拟的渤南北带致密砂砾岩体内幕结构解剖

Inside Structure Anatomy of Dense Sand Gravel Mass in North Belt of Bonan SAG Based on Forward Modeling

渤南北带近岸水下扇致密砂砾岩体内幕地震反射特征复杂,沉积期次划分困难,严重制约了成熟盆地油气高效勘探开发。为此,通过井震结合,分析影响砂砾岩体地震反射内部结构的地质因素主要为不同砂砾岩体的速度差异和砂砾岩体之间的泥岩隔层厚度。采取控制变量法,开展砂砾岩体内部结构正演模拟,结果表明,不同的砂砾岩体之间的速度差越大,地震反射越强;两套砂砾岩之间泥岩隔层越厚,地震反射结构差异越明显;同时开展近岸水下扇前端强反射正演模拟,发现厚层泥岩中的薄层砂岩,结合实钻井岩性特征,发现了浊积岩。最终建立了渤南北带近岸水下扇–浊积岩沉积体系,为油田高效勘探开发提供借鉴。

The tight glutenite in the nearshore subaqueous fan of the lower Es3 in the steep slope zone of the BonanSubsag is characterized by very complex inner seismic reflection, which induces difficulties in the division of sedimentary periods. And thus this seriously restricts the efficient exploration and development of oil and gas in the mature basins. By the analysis of well-seismic combination, it is considered that the geological factors affecting the internal structure of seismic reflection of sandy conglomerate are mainly the velocity difference of different sandy conglomerate and the thickness of mudstone interlayer between sandy conglomerate. Therefore, the control variable method was adopted to carry out the forward modeling of the internal structure of sandy conglomerate. The results show that the greater the velocity difference between different sandy conglomerates results in the stronger the seismic reflection. Meanwhile, there is a strong positive correlation relationship between the thick of the mudstone interlayer between the two sets of glutenite and the difference of seismic reflection structure. The forward modeling of strong seismic reflectionstructureat the front end of nearshore subaqueous fan illustrates the existence of thin sandstone in the thick mudstone, which is identified as turbidite by the combined analysis of lithology characteristics of the drilled cores. The seismic reflection structure model of the nearshore subaqueous fan-turbidite sedimentary system in the steep slope zone of the Bonansubsag is established, aiming to provide reference for efficient exploration and development of oil field.